Among refractory products, a distinction is made between fused-cast products and sintered products. In contrast to sintered products, fused-cast products most often comprise a very abundant intergranular vitreous phase, filling the network of crystalline grains. The problems encountered in their respective applications in the case of sintered products and in the case of fused-cast products, and the technical solutions adopted for solving them, are therefore generally different. Moreover, owing to the large differences between the manufacturing processes, a composition developed for making a fusion-cast product is not a priori usable as such for making a sintered product, and vice versa.
Sintered products are obtained by mixing suitable raw materials and then crude forming of this mixture and baking of the resultant crude article at a temperature and for a time sufficient to obtain sintering of said crude article. The sintered products are intended for very varied industries, depending on their chemical composition.
Refractory products comprising chromium oxide are used conventionally in applications where they are subject to extreme chemical aggression, for example in glass furnaces, in particular as furnace tank blocks, or in furnaces in which they are in contact with slag, or in garbage incinerators.
In these applications, mechanical and thermal stresses can also be severe. Thermal cycling (repeated increases and decreases in temperature) can in particular generate cracks, which will reduce the mechanical strength of the refractory products. These cracks can also be a preferred path for aggressive agents.
The use of said refractory products in contact with slag or with molten glass is known for example from U.S. Pat. No. 6,352,951 (incinerating furnaces containing blocks based on alumina and chrome) and from U.S. Pat. No. 4,823,359 (glass furnaces with linings consisting of alumina and chrome). The corrosion due to a slag is different from the corrosion caused by molten glass and therefore a product suitable for being brought in contact with slag is not necessarily suitable for an application in which it would come in contact with molten glass.
There is a constant need for new refractory products based on chromium oxide having good resistance to thermal shock and high corrosion resistance, notably in an application in which these products are brought in contact with molten glass.
One aim of the invention is to meet this need.